The invention relates to an airbag, a method for folding same and a device for carrying out the method.
In order to be able to store an airbag in an airbag module, it is known to fold the airbag into a correspondingly small packet. Different types of folding are known. Thus, from U.S. Pat. No. 4,173,356, different types of straight line folding are known, wherein the folds run in rays from a center towards the outside or approximately parallel to each other. The drawback with these folds is that they have to be collapsed at least when used in a driver airbag module so that during unfolding of an airbag of this kind, the internal pressure produced in partial areas of the airbag impede the opening of some folds. Furthermore, the expense of folding is considerable.
German Patent publication DE 44 22 276 A1 discloses an airbag for an airbag module having main folds that run at least in part along closed tracks round an imaginary center on the substantially empty spread-out airbag. The closed main folds describe preferably circular paths or ellipses of slight eccentricity.
This path for the main folds has the advantage that the folded airbag can open very rapidly and easily. More particularly during the unfolding of such an airbag there is not the danger that the internal pressure produced in partial areas of the airbag will prevent the opening of further folds. This airbag can thereby be used for driver, passenger and side airbags. The drawback with this folding is that the expense for mechanical folding is high.
The object of the present invention is to fold the airbag so that on the one hand it can be easily and completely unfolded and on the other the expense of folding the airbag is reduced.
According to the invention, the airbag has in the folded position at least one continuous constriction as well as ordered and/or chaotic folds. More particularly, it is proposed that the folds in the areas of the airbag divided by the constriction run separated without overlapping the constriction. In the case of an airbag with a top and bottom side, the constriction extends from the top side to the bottom side of the airbag. More particularly, the constriction extends in one embodiment at right angles to the plane of the spread-out unfolded airbag through same.
The advantage of this constriction is that it has a positive effect particularly on the chaotic folding. The drawback of chaotic folding, where the unfolding of the airbag is impeded in the areas where the airbag overlap, is substantially avoided by the provision of at least one constriction. Furthermore, there is the advantage that for different shapes of airbag modules, through one or more constrictions, it is possible to spread out the folds to match the different shapes. The space available for the folded airbag can be utilized in an optimum manner.
Depending on the selected form of the spread-out airbag, it can be expedient to provide one, two or more constrictions in the airbag. The airbag for a driver airbag module preferably has four constrictions.
In a further embodiment, at least one constriction is provided which runs between the upper side and the lower side of the airbag. With this embodiment owing to this constriction, the upper and lower parts of the airbag are separated at least in part, and both parts also have separate folds. With this embodiment, the fact that the folds of the upper part do not project into the folds of the lower part has a particularly advantageous effect on the all-round rapid unfolding of the airbag. Furthermore, with the constriction, the outer areas of the airbag are moved inwards close to the gas generator or diffuser. Thus, during unfolding of the airbag, apart from the accelerated expansion in the main unfolding direction, an expansion at right angles thereto is also achieved. By selecting the arrangement, number and depth of the constrictions it is possible to accurately control the unfolding in certain directions.
One method for folding an airbag is characterized according to the invention in that the spread-out airbag is constricted at least once continuously on at least one side and that it is then folded and/or compressed to the extent required for stowage in the airbag module.
It is expedient if the airbag is folded separately in areas which are separated by a constriction.
In a first embodiment in the case of an airbag which has an upper side and a lower side, the airbag is constricted from the upper to the lower side.
The constriction carried out in the first stage represents a pre-folding for the following orderly or chaotic folding. These method steps allow a simple mechanical conversion since the production of a constriction and the compression of the thus pre-folded airbag are simple procedures.
The airbag is preferably constricted at right angles to the plane of the spread-out airbag. However constrictions deviating from the perpendicular are also possible to obtain the advantages.
The airbag is constricted on one side or on several sides. The airbag for a passenger airbag module is preferably constricted from one side. The spread-out airbag, which is only provided with the one constriction, has prior to compression the shape of a human molar tooth with two roots.
The airbag for a driver airbag module is preferably constricted on four sides, preferably simultaneously. The spread-out airbag, which is only provided with the four constrictions, has prior to compression the shape of a four-leaved clover.
During folding and compression of the airbag, the constrictions previously provided have the effect that the ordered and/or chaotic folds produced are each only formed inside the area defined by the constrictions, i.e. the folds do not overlap the constrictions. Overlapping of in particular the chaotic folds is thereby substantially avoided. The constrictions are also obtained after the chaotic folding.
In a further embodiment it is proposed that the airbag is constricted between its upper and lower side and that then both sides are folded and/or compressed separately.
A device for folding an airbag is characterized according to the invention in that one tool each is provided for producing each constriction, that the spread-out airbag and the tool can be moved relative to each other in the plane of the spread-out airbag and that folding tools and/or slider-like tools for compressing the airbag to the storage size are provided above and/or at the side of the spread-out airbag.
In one embodiment it is proposed that the tool for producing a constriction extends perpendicular to the plane of the spread-out airbag. The tool preferably extends at least over the height of the airbag in its folded position.
In a further embodiment it is proposed that the tool for producing a constriction extends parallel to the plane of the spread-out airbag. In this embodiment the width of the tool is preferably less than the largest width measurement of the spread-out airbag.
A sword-like tool can advantageously be provided for producing the constriction. This tool has at least a height corresponding to the proposed height of the folded airbag so that the airbag is constricted over the entire height when sliding the tool sideways into the airbag.
In a further embodiment a wire-like tool is provided for producing the constriction and extends substantially at right angles to the spread-out airbag.
In preferred embodiments it is proposed that one sword-like or wire-like tool each is provided for producing each one constriction.
It is expedient for the prefolding of an airbag for a passenger airbag module to provide a tool so that a constriction is produced during its operation. For prefolding an airbag for a driver airbag module it is expedient to provide four tools so that when operated four constrictions are produced.
These sword or wire like tools as well as the slider-like tools for compressing the airbag are to be operated mechanically and simply in any known way whereby a high processing reliability is achieved.
A further design of the tool is characterized in that a space is provided for folding the airbag between a lower cover plate and an upper cover plate of which one is movable, that the sword-like tool runs between the cover plates and at right angles to same, that the space for folding the airbag is restricted at the side by sliders which are displaceable between the cover plates, that in the lower cover plate an opening is provided for an airbag housing and next to this at least one slider is provided which can be moved at right angles relative to the cover plates, and that in the upper cover plate in the area of the airbag housing an opening is provided in which a removable packing ram is mounted which can be moved at right angles to the cover plates and contains a place holder which can be moved perpendicular to the cover plates.
The place holder has, at right angles to the direction of movement, roughly the cross-sectional shape of a flue of a diffuser inserted in the airbag housing.
The invention will now be explained in further detail with reference to the embodiments shown in the drawings.